1. Field of the Invention
The present invention relates to a power station installation in accordance with the preamble of claim 1. It also relates to a process for operating such an installation.
2. Discussion of Background
The HTR (high-temperature reactor) promises the highest possible safety potential and very good utilization of the fissile materials. Accordingly, the declared aim is to make it feasible. Numerous studies have shown that the investment costs to obtain economic efficiency in a cross comparison with other concepts are at present still very high.
If a direct cycle installation is desired, i.e. a helium turbine cycle integrated into the reactor cooling section, very high costs result, since all components of this helium cycle must, for safety reasons, be enclosed in a pressure vessel made, for example, of prestressed concrete. These components comprise the helium turbine set, the recuperator, the precooler and, if appropriate, an intercooler, as well as the extensive connecting lines and valves for control. A particular hazard potential in a gas turbine system integrated into the cooling cycle of the reactor core are possible large pressure transients in the event of an internal fracture of a coaxial line, of a support plate of a heat exchanger or of spontaneous blade loss of turbine or compressor. Such pressure transients could put internal insulations, liners and core internals at a mechanical risk. However, water ingress in the event of a defective precooler or intercooler also represents a hazard potential which can hardly be ignored.
Another solution according to the state of the art is the so-called two-cycle installation. In this case, helium as the reactor coolant is circulated by means of fans and the thermal reactor output is thus transferred to steam generators integrated on the primary side. In this case, the risk of pressure transients is largely averted, because the cooling circulation has no large pressure differences between its components reactor, fan and steam generator heating surfaces. The risk of an ingress of steam or water into the primary cycle is, however, rather greater than in the case of the direct helium turbine cycle, because the pressure of the steam or water far exceeds that of the helium.
One solution, advantageous in safety terms, would be a separation of the primary reactor cooling cycle from the secondary conversion cycle by a helium/helium heat exchanger. This would be integrated together with the helium circulation fans and the reactor core into a steam vessel. The conversion cycle would be a helium turbine system. However, in such an arrangement, the achievable efficiency of the conversion of the thermal reactor output into electric power would be relatively low, because the helium turbine can be subjected only to about 800.degree. C. This and the high specific costs of a helium turbine installation with a necessarily highly efficient recuperator and intercooling of the compression are obstacles to the implementation of such a solution.